The invention concerns an electrical-wiring duct to ensure future power and communications, with electrical potential between its cover and housing compensated.
A wall-mounted duct with a metal base that accommodates electrical wiring is known from German GM 8 70 4502. It consists essentially of structural C section, open along one side. The opening is closed off by a cover that is also made of metal. Along the edges of the duct are grooves that the cover can snap into. The grooves also contain metal clips with prongs integrated into them that come into contact in the grooves and against the cover when the duct is closed up. The contact produces an electrical connection between the base and the cover. The prongs are in the form of loops and are intended to penetrate any enamel or lacquer on the base. The design facilitates mounting the cover on and removing it from the base without damaging either component. One drawback to such a duct is that the base and cover cannot be enameled or surface-coated while together. Another drawback is that the metal clips require an additional component, which means extra installation expense and does not ensure that they can be removed.
German GM 8 704 502 discloses a duct for accommodating electric wiring that is also especially appropriate for accommodating electrically conductive strips and adapters. This duct is essentially metal structural U section with each side bent in to create a support for the cover that closes it off. The cover is accordingly locked into electrical contact with the base and can be released from it. Another duct for accommodating electrical conductors is known from German GM 7 701 100. Both the U-sectional base and the cover are also metal, snap together to create an electrical connection, and can be separated. Snap-in ribs in the form of strips are provided for this purpose along the inner surface of the cover, project into the vicinity of the cover's edge, and are secured by engaging the bent-in areas. The connection and contact is further promoted by clips in the form of springs. Since the springs do not extend through the total length of the projection, however, it is impossible to prevent paint from penetrating when the duct is painted and damaging the contact.
German GM 8 806 713 discloses a duct of metal essentially U section with bent-in areas. The cover is secured to the base by two snap-in ribs extending out in the form of continuous strips from the inner surface of its edges and engaging the U section. The edges of the cover, however, rest against the bent-in areas.
German OS 2 516 404 discloses a duct with a U-sectional base and a cover, both of which may be metal. Like another embodiment that has been applied for, it has already-known covers with two longitudinal projections or snap-in ribs that rest against each other along the base, leaving a space that can protect the contact surface inside the housing from penetrating paint. The outer edge of the cover, however, rests against the sectional base.
German GM 7 701 076 describes a cable duct of several connecting sections. The cover is secured together by additional difference-compensating clips inside the longitudinal side of the groove. This type of connection is intended to eliminate play between the separate sections of duct and its cover. The clips, however, are made of such an elastic material as plastic or rubber. Another objective is to eliminate clicking.
German OS 3 516 149 discloses a cable-duct section for laying wires. All the components of this duct are interchangeable and can be connected by simple snap-together connectors.
All the aforesaid disclosure address cable duct or current-conductive strip protected by a closure (cover or wall). It is precisely this type of duct that is often made of plastic. When on the other hand they are made of metal, they are surface-coated to improve their appearance. The coating can be spray-painted or applied electrostatically. Such a coating, however, makes it impossible to ensure metallic contact between the duct's housing and cover. This situation does not comply with existing standards with respect to malfunction.